Test D - Act Sensor

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: cooling system, improper engine oil level, air cleaner duct problem. Ambient air temperature must be at least 50°F (10°C) for test results to be valid. Avoid performing test in unusually hot or cold conditions.

1. Code 24 Displayed. For vehicles with ACT sensor mounted in intake manifold, go to next step. If sensor is properly mounted in air cleaner on all other models, go to next step. If sensor is not properly mounted, install ACT sensor properly and repeat QUICK TEST  .
2. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale and disconnect Throttle Position Sensor (TPS). Turn key on, leaving engine off. Measure voltage between VREF and signal return at TPS connector. If reading is less than 4.0 volts or more than 6.0 volts, go to TEST C - REFERENCE VOLTAGE  , Step 1). If reading is between 4.0 and 6.0 volts, connect TPS and go to next step.
3. Start engine and make sure that engine reaches normal operating temperature. Turn key off and wait 10 seconds. Disconnect ACT sensor, set DVOM on 200,000-ohm scale, and measure ACT sensor resistance. If reading is less than 1100 ohms or more than 58,000 ohms, check function of heat stove duct valve. If valve is operating correctly, replace ACT sensor, connect ACT sensor, and repeat QUICK TEST  . If reading is between 1100 and 58,000 ohms, go to next step.
4. Turn key off. Disconnect ACT sensor harness. Set DVOM on 200,000-ohm scale and run engine for 2 minutes. While engine is running, measure ACT sensor resistance. If reading is between 2400 and 29,000 ohms, replace ECA, connect ACT harness, and repeat QUICK TEST  . If reading is less than 2400 ohms or more than 29,000 ohms, check function. If valve works properly, replace ACT sensor. Repeat QUICK TEST  .
5. Code 54 Displayed. Turn key off and wait 10 seconds. Disconnect ACT sensor harness. Inspect for and repair any damaged wiring. Install a jumper wire between ACT signal and signal return at connector. Perform KEY ON/ENGINE OFF SELF-TEST  . If code 64 is displayed, replace ACT sensor. Remove jumper wire, connect ACT sensor, and repeat QUICK TEST  . If code 64 is not displayed, remove jumper wire and go to next step.
6. Turn key off and wait 10 seconds. Leave ACT sensor harness disconnected. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between test pin 25 and ACT signal at ACT connector, and between test pin 46 and signal return at ACT connector. If both readings are less than 5 ohms, replace ECA and remove breakout box. Connect ECA and ACT sensor, then repeat QUICK TEST  . If either reading is 5 ohms or higher, repair opens in circuit. Remove breakout box, connect ECA and ACT sensor. Repeat QUICK TEST  .
7. Code 64 Displayed. Turn key off and wait 10 seconds. Disconnect ACT sensor. Inspect for and repair any damaged wiring. Perform KEY ON/ENGINE OFF SELF-TEST  . If code 54 is displayed, replace ACT sensor, connect harness, and repeat QUICK TEST  . If code 54 is not displayed, go to next step.
8. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale and disconnect TPS. Turn key on, leaving engine off. Measure voltage between VREF and signal return at TPS connector. If reading is less than 4.0 volts or more than 6.0 volts, go to TEST C - REFERENCE VOLTAGE  , Step 1). If reading is between 4.0 and 6.0 volts, connect TPS and go to next step.
9. Turn key off and wait 10 seconds. Disconnect harness at ACT sensor. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box and set DVOM on 200,000-ohm scale. Measure resistance between test pin 25 and test pins 40, 46, and 60. If any reading is less than 10,000 ohms, repair shorts. Remove breakout box, connect ECA and ACT sensor. Repeat QUICK TEST  . If all readings are 10,000 ohms or higher, replace ECA. Remove breakout box, connect ECA and ACT sensor. Repeat QUICK TEST  .
10. Continuous Code 54 or 64 Displayed. Using CONTINUOUS MONITOR (WIGGLE) TEST  , observe VOM or STAR tester LED for indication of fault while tapping ACT sensor lightly and wiggling connector. If fault is indicated, inspect connector and terminals. If connector and terminals are good, replace ACT sensor and repeat QUICK TEST  . If no fault is indicated, go to next step.
11. While in CONTINUOUS MONITOR (WIGGLE) TEST  , wiggle and bend small sections of harness from ACT sensor to firewall. Repeat action from firewall to ECA. If fault is indicated, isolate fault and repair as necessary. Repeat QUICK TEST  . If no fault is indicated, go to next step.
12. Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect both connector and connector terminals for obvious damage. If connector and terminals are damaged, repair as necessary and repeat QUICK TEST  . If connector and terminals are okay, fault cannot be duplicated at this time, continuous code 54 or 64 testing is complete.

Fig 1: Air Charge Temperature (ACT) Sensor Circuit